Device for pivotably connecting parts of an orthopaedic device

ABSTRACT

The invention relates to a device for pivotably connecting parts of an orthopaedic device, such as in particular a prosthetic knee for leg amputees, which device comprises a kinematic multibar mechanism with at least four bars, which bar mechanism allows a movement in the walking direction (L), in which device—a first bar can be connected to a first part of the orthopaedic device, such as a thigh socket,—a second bar can be rigidly connected to a second part of the orthopaedic device, such as a lower-leg part,—a third bar, which is arranged at the front as seen in the walking direction (L), is pivobably connected to the first bar and is pivotably connected to the second bar,—a fourth bar, which is arranged behind the third bar as seen in the walking direction, is pivotably connected to the first bar and is pivotably connected to the second bar, in such a manner that the connection between the second bar and the fourth bar can be displaced along an imposed path, and—a centre part of the fourth bar, lying between the two ends of the fourth bar, being connected to the third bar, in such a manner that the connection between the third bar and the centre part can be displaced along an imposed path.

[0001] The invention relates to a device for pivotably connecting partsof an orthopaedic device, such as in particular a prosthetic knee forleg amputees.

[0002] The use of multibar mechanisms to replace or assist the jointfunction in orthopaedic devices has already been known for some time andis widely used on account of the advantages of a mechanism of this typeover the more conventional mechanisms with one fixed pivot point. Theseadvantages include, inter alia, better following or simulation of thenatural movement of the limbs compared to a single-axis mechanism, andenhanced and more easily controllable stability of the mechanism when itis subject to load, and these advantages are achieved by suitableselection of the dimensions and the position of the bars of themechanism with respect to one another. Particularly when a multibarmechanism is used to replace or assist the knee function, the latterfactor is of great importance. This is because it is desirable, at thestart of a step, when the mechanism is extended, the heel comes intocontact with the ground and the mechanism is loaded by the weight of theuser, for the mechanism not to start to pivot immediately, since thiswould not provide the user with any support, and consequently the userwould fall over. In a single-axis mechanism, this can only be preventedby using a complex, relatively unreliable braking mechanism. Bycontrast, in a multibar mechanism this property can be achieved, forexample, by selecting the geometry in such a way that, in the extendedstate of the mechanism, the virtual rotation point about which the lowerleg or the lower-leg prosthesis pivots lies behind the line whichconnects the two points of load (the heel and the hip joint).

[0003] Moreover, by suitably selecting the geometry of the multibarmechanism, it is possible to achieve the effect whereby the virtualrotation point, at the end of a step, is located in such a way that theprosthesis or orthesis can more easily be made to execute a forwardlyswinging movement than a single-axis mechanism. The high level ofstability which can be achieved at the start of the step, theswinging-back movement which is easy to generate and the possibility of,in a simple way, finding a good compromise between these two propertiesmake the multibar mechanism eminently suitable for replacing orsupporting a joint function.

[0004] In applications of this nature, a kinematic multibar mechanismmay exhibit initial yielding bending. This is desirable for somepatients.

[0005] Particularly in what is known as a “knee disarticulation”(amputation of the leg at the joint), the existing devices have thedrawback that the bending angle is insufficient. In addition, the thighis unnaturally lengthened, which in the sitting position leads to anunnatural shape of the leg.

[0006] It is an object of the invention to provide a device which hasthe following characteristic features:

[0007] adjustability in order, if desired, to obtain a high level ofstability when load is applied to the heel,

[0008] a decrease in the stability under front-foot loading at the endof the standing phase, so that the prosthesis can easily be made toswing,

[0009] if appropriate, initial yielding, resulting in a damping actionfor the load on the prosthesis and therefore on the thigh stump, a verylarge maximum bending angle,

[0010] a very minor lengthening in the position in which the prosthesisis bent through 90°,

[0011] a cosmetically natural 90° position, and

[0012] simplicity of design and reliability in use. To this end, theinvention provides a device, which device comprises a kinematic multibarmechanism with at least four bars, which bar mechanism allows a movementin the walking direction (L), in which device:

[0013] a first bar can be connected to a first part of the orthopaedicdevice, such as a thigh socket,

[0014] a second bar can be rigidly connected to a second part of theorthopaedic device, such as a lower-leg part,

[0015] a third bar, which is arranged at the front as seen in thewalking direction (L), is pivotably connected to the first bar and ispivotably connected to the second bar,

[0016] a fourth bar, which is arranged behind the third bar as seen inthe walking direction, is pivotably connected to the first bar and ispivotably connected to the second bar, in such a manner that theconnection between the second bar and the fourth bar can be displacedalong an imposed path, and

[0017] a centre part of the fourth bar, lying between the two ends ofthe fourth bar, being connected to the third bar, in such a manner thatthe connection between the third bar and the centre part can bedisplaced along an imposed path.

[0018] A device of this type according to the invention provides therequired functionality and a relatively high stance flexion incombination with limiting a second degree of freedom of movement, whichis easy to achieve.

[0019] According to a preferred embodiment of the device according tothe invention, the device comprises a fifth bar, which is pivotablyconnected to the fourth bar and to the second bar.

[0020] Another preferred embodiment of the device according to theinvention comprises a sixth bar, which is pivotably connected to thefourth bar and to the third bar. The use of a fifth and sixth bar ispreferred, since this creates a device which is of simple design and isreliable in use.

[0021] In yet another embodiment of the device according to theinvention, at least one of the connections which can be displaced alongan imposed path is a tongue-and-groove connection.

[0022] In this case, the imposed path may, if appropriate, be circular.

[0023] In a preferred embodiment of the device according to theinvention, the pivot points between the sixth bar and the third andfourth bars lie at a distance from the ends of the third and fourthbars, respectively. It has been found that positioning the pivot pointsin this way allows the desired functionality to be achieved for a devicewhich is used as knee pivot.

[0024] In yet another preferred embodiment of the device according tothe invention, the device comprises spring means which are arrangedbetween two bars of the multibar mechanism. The spring means can beused, for example, to facilitate moving the lower leg forward at the endof the swinging phase. In addition, the spring means may also comprisedamping means. This enables energy to be dissipated in the swingingphase, so that the device moves smoothly into the extended position.This increases comfort for the user.

[0025] In one embodiment of the device according to the invention, thedimensions of the multibar mechanism are selected in such a manner thatthe device can be pivoted between the first, blocking position and asecond position. The first, blocking position is intended to mean theposition of the device in which stance flexion is achieved, while thesecond position is intended to mean the position of the device in whichswing flexion is possible.

[0026] Preferably, the device is designed in such a manner that, duringdisplacement of the vertical load on the device in the walking direction(L), the device pivots out of the blocked position into the secondposition. This allows natural walking when using the device.

[0027] In yet another preferred embodiment of the device according tothe invention, the device comprises at least one stop for stopping a barin order to define the blocking position. It is preferable for the stopto be adjustable. This allows the action and functionality of the deviceto be adjusted.

[0028] Furthermore, the device according to the invention may comprisespring means which act in the direction of the blocking position inorder, at least in the blocking position of the device, to create aresilient action between the first part and the second part of theorthopaedic device. In this case, it is preferable for the stop to bemade from a resilient material. As a result, in the blocking positionthere is a resilient action which increases comfort.

[0029] Finally, in an embodiment according to the invention, at leastone of the bars may be of multiple design. This increases the torsionalrigidity of the device.

[0030] These and other characteristics of the device are explained inmore detail with reference to the appended drawings, in which:

[0031]FIG. 1 shows a perspective view of a thigh prosthesis using adevice according to the invention, in this case designed as a kneepivot,

[0032]FIG. 2 shows a side view of the knee pivot shown in FIG. 1,

[0033]FIGS. 3a-3 c show three different positions of the knee pivotduring a step,

[0034]FIGS. 4a and 4 b show the thigh prosthesis shown in FIG. 1 in thesitting position,

[0035]FIG. 5 shows a second embodiment of a device according to theinvention,

[0036]FIG. 6 shows a third embodiment of the device according to theinvention,

[0037]FIGS. 7a to 7 d diagrammatically depict various positions forfitting a resilient stop in a device according to the invention,

[0038]FIGS. 8a-8 c show various positions for fitting a resilient damperin a device according to the invention.

[0039]FIG. 1 shows a thigh prosthesis having a device according to theinvention which is designed as a knee pivot 1. This knee pivot 1comprises a multibar mechanism, in which means for securing to a thigh,such as a thigh socket 2, are arranged on the first bar 11. A lower-legpart 3 with an artificial foot 4 is arranged on a second bar 12 of theknee pivot 1.

[0040]FIG. 2 shows the knee pivot 1 according to the invention in moredetail. It can be seen once again that the first bar 11 of the multibarmechanism is connected to the thigh socket 2 and that the second bar 12is connected to the lower-leg part 3. In the walking direction L, athird bar 13 is arranged pivotably at the front side between the firstbar 11 and the second bar 12. Furthermore, a fourth bar 14 and a fifthbar 15 are arranged behind the third bar 13, as seen in the walkingdirection L, which fourth and fifth bars 14, 15 are pivotably connectedto one another on one side and on the other side are pivotable connectedto the first bar 11 and the second bar 12, respectively.

[0041] Finally, a sixth bar 16 is arranged pivotably between the thirdbar 13 and the fourth bar 14. The pivot points 17 and 18 of this sixthbar lie at a distance from the ends of the third bar 13 and the fourthbar 14, respectively. The ends of these bars 13 and 14 are understood tomean the pivot points arranged at these ends. Furthermore, in the kneepivot 1 there is a damper 5, which is connected, by means of a pistonrod 6, to one of the bars of the bar mechanism, in this case to a fourthbar 14.

[0042] A stop 19 is fitted in order to limit the travel of the bar 15.

[0043] The operation of the knee joint 1 according to the invention isexplained in more detail with reference to FIGS. 3a to 3 c.

[0044]FIG. 3a shows the position of the knee pivot 1 when the thighprosthesis is at the start of the step, i.e. the position in which theartificial foot 4 is situated in front of the other foot. The verticalload B acting on the knee joint 1 lies behind the knee joint 1, as seenin the walking direction L. The fifth bar 15, and therefore the entiremechanism, is now in the blocked position, with the result that the kneepivot 1 is fixed and the thigh prosthesis can commence the step.

[0045]FIG. 3b shows the position in which the vertical load B acting onthe knee joint 1 has shifted to in front of the knee joint 1. Thisposition preferably corresponds to the situation in which the verticalload vector B intersects the front side of the artificial foot 4. Thiscorresponds to the situation in which the user is standing on the “ballof the foot”. At this moment, the fifth bar 15 pivots out of the blockedposition, as shown in FIG. 3a, into a second position.

[0046]FIG. 3c shows the fifth bar 15 in the second position, so that thelower-leg part 3 can enter the swinging phase. At this time, theartificial foot 4 is no longer in contact with the ground and the thighprosthesis can be swung into the position which correspond to that shownin FIG. 3a.

[0047]FIGS. 4a and 4 b show the sitting position of the knee pivot 1. Acharacteristic feature of the knee pivot 1 according to the invention isthat, in the sitting position of the device, it adopts a shape which issuch that the appearance of the leg with the prosthesis corresponds tothat of a leg without prosthesis. It is clearly evident from FIG. 4bthat the third bar 13 of the knee joint 1 runs virtually parallel to thefront side of the lower-leg part 3.

[0048]FIG. 5 shows a second embodiment 20 of a device according to theinvention. This device largely corresponds to the knee pivot 1 shown inFIG. 1. Therefore, identical parts are provided with identical referencenumerals. It is clearly apparent that a first bar 11 is connected to athigh prosthesis, while a second bar 12 is connected to a lower-leg part3. A third bar 13, which is pivotably connected at each end, runsbetween this first bar 11 and second bar 12. Furthermore, a fourth bar14 is arranged pivotably on the first bar 11, the other end of whichfourth bar 14 is pivotably connected to a fifth bar 15, which in turn isconnected to the second bar 12. Also, a sixth bar 16 runs between thefourth bar 14 and the third bar 13.

[0049] The difference from the device shown in FIG. 1 is that, insteadof pivot pins, in this case ball-and-socket joints 21 are used topivotably connect the fifth bar 15 and the sixth bar 16. The advantageof these ball-and-sockets joints is that the mechanism will stilloperate despite any manufacturing tolerances. In fact, if a device 1 asshown in FIG. 1 is not manufactured with sufficient accuracy, there is arisk that the mechanism will fail to operate entirely.

[0050]FIG. 6 shows a third embodiment of a device according to theinvention. In this case too, identical parts are denoted by identicalreference numerals. The difference from the two embodiments 1 and 20above is that there are no fifth and sixth bars. Instead, the fourth bar14 is connected to the second bar 12 by means of a tongue-and-grooveconnection. This tongue-and-groove connection comprises a tongue 31,which is arranged at the end of the fourth bar 14, and a curved groove32 arranged in the second bar 12.

[0051] Furthermore, the fourth bar 14 is connected to the third bar 13by means of a tongue-and-groove connection. For this purpose, a secondtongue 33 is arranged on a centre part of the fourth bar 14 and runs ina groove 34 arranged in the third bar 13.

[0052] It will be obvious that where the tongues 31 and 33 are arranged,they may be replaced by a groove, while the grooves 32, 34 are replacedby a tongue.

[0053]FIGS. 7a to 7 d diagrammatically depict a device which correspondsto the knee pivot 1 shown in FIG. 1. Therefore, identical parts are onceagain denoted by identical reference numerals. These four figures showfour different positions for a resilient stop which comprises a stoppart 40 and a resilient element 41. As is shown in the figures, thisresilient stop may, for example, be arranged between the second bar 12and the fifth bar 15 (FIG. 7a), between the fourth bar 14 and the sixthbar 16 (FIG. 7b), between the first bar 11 and the fourth bar 14 (FIG.7c) or between the third bar 13 and the sixth bar 16 (FIG. 7d). However,the design shown in FIG. 7a is preferred.

[0054]FIGS. 8a to 8 c show various positions for a resilient damper. Inthis case too, the bar mechanism corresponds to the mechanism of thedevice shown in FIG. 1, and therefore identical parts are once againdenoted by identical reference numerals. The resilient damper isdiagrammatically indicated by a damping element 42 and a spring 43. Thisassembly 42, 43 may, for example, be positioned between the second bar12 and fifth bar 15 (FIG. 8a), the fourth bar 14 and the second bar 12or with the lower-leg part 3 arranged fixedly thereon (FIGS. 8b and 8c). The diagrammatic structure shown in FIG. 8b corresponds to the kneepivot shown in FIG. 1 and is therefore preferred.

1. Device for pivotably connecting parts of an orthopaedic device, suchas in particular a prosthetic knee for leg amputees, which devicecomprises a kinematic multibar mechanism with at least four bars, whichbar mechanism allows a movement in the walking direction (L), in whichdevice a first bar can be connected to a first part of the orthopaedicdevice, such as a thigh socket, a second bar can be rigidly connected toa second part of the orthopaedic device, such as a lower-leg part, athird bar, which is arranged at the front as seen in the walkingdirection (L), is pivotably connected to the first bar and is pivotablyconnected to the second bar, a fourth bar, which is arranged behind thethird bar as seen in the walking direction, is pivotably connected tothe first bar and is pivotably connected to the second bar, in such amanner that the connection between the second bar and the fourth bar canbe displaced along an imposed path, and a centre part of the fourth bar,lying between the two ends of the fourth bar, being connected to thethird bar, in such a manner that the connection between the third barand the centre part can be displaced along an imposed path.
 2. Deviceaccording to claim 1, wherein the device comprises a fifth bar, which ispivotably connected to the fourth bar and to the second bar.
 3. Deviceaccording to claim 1 or 2, wherein the device comprises a sixth bar,which is pivotably connected to the fourth bar and to the third bar. 4.Device according to claim 1 or 3, in which at least one of theconnections which can be displaced along an imposed path is atongue-and-groove connection.
 5. Device according to one of thepreceding claims, in which the imposed path is a circular path. 6.Device according to claim 3, in which the pivot points between the sixthbar and the third and fourth bars lie at a distance from the ends of thethird and fourth bars, respectively.
 7. Device according to one of thepreceding claims, comprising spring means which are arranged between twobars of the multibar mechanism.
 8. Device according to claim 7, in whichthe spring means comprise damping means.
 9. Device according to one ofthe preceding claims, in which the dimensions of the multibar mechanismare selected in such a manner that the device can be pivoted between afirst, blocking position and a second position.
 10. Device according toclaim 9, in which, when the vertical load of the device is displaced inthe walking direction (L), the device pivots out of the blocked positioninto the second position.
 11. Device according to claim 9 or 10,comprising at least one stop for stopping a bar so as to define theblocking position.
 12. Device according to claim 11, in which the stopis adjustable.
 13. Device according to claim 9, 10 or 11, comprisingspring means, which act in the direction of the blocking position, forcreating, at least in the blocking position of the device, a resilientaction between the first part and the second part of the orthopaedicdevice.
 14. Device according to claims 11 and 12, in which the stopcomprises a resilient material.
 15. Device according to one of thepreceding claims, in which at least one of the bars is of multipledesign.